1. Field of the Invention
The present invention is concerned with the production of wood curls for various applications, such as potpourri, packing material and animal litter. The apparatus of the invention employs a parallel to the wood grain, orthogonal cutting action at substantially low rake angles to form curled wood shavings. The invention permits adjustments so as to produce wood curls with different characteristics suitable for various applications.
2. Description of Prior Art
Myriad devices and methods for wood machining are known. Two basic processes predominate this art. A first process known as peripheral milling is largely concerned with manipulating the work piece to a desired shape and surface. Peripheral milling involves a rotary cutting process in which wood is removed in the form of single chips. The chips are formed by the intermittent engagement of the work piece by knives carried on the periphery of a rotating cutter head. The finished surface therefore consists of a series of individual knife traces generated by the successive engagement of each knife. A single surfacer with rotating cutter head illustrates the peripheral milling process.
A second process, employed by this invention, is known as orthogonal cutting. This process is primarily concerned with producing wood chips or flakes for various applications. In orthogonal cutting, the cutting edge is perpendicular to the direction of the relative motion of tool and work piece and the surface generated is in a plane parallel to the original work surface. A carpenter's hand plane illustrates orthogonal cutting.
Orthogonal cutting is utilized in various chipping machines. Such machines reduce pulpwood to more or less uniform chips required to manufacture chemical pulp. The uniform chips permit cooking liquor to penetrate the wood quickly, completely, and uniformly. Most chippers include a heavy rotating steel disc that is slotted on the face to receive chipping knives. Wood is presented to the rotating disc so that the knives remove chips. Wood chippers typically have a cutting action whereby the knives cut essentially through a cross section of the wood fibers to produce a flat, rough product. Orthogonal cutting is further utilized in wood flaking machines. Such machines cut flakes of more or less controlled dimensions. These flakes, or particles, are used in making particle board.
The design of flakers is influenced by the form of the raw material introduced to the equipment, moisture content of the wood, the shape of flake desired, and the rate of production required. Peripheral milling, lathe, and disc type flakers are well described in the art.
A key factor in determining the shape of a chip or flake is the rake angle. In the nomenclature of wood machining, the rake angle is often defined as the angle made between the tool face and a plane perpendicular to the direction of tool travel. Rake angle is also sometimes referred to as the hook angle, the chip angle, or the angle of attack. The pulp and paper and particle board industries require flat chips and flakes. The prior art and literature teach the use of rake angles in the range of forty-five degrees to sixty degrees (45.degree.-60.degree.) to produce flat wood particles and teach away from the production of curled flakes.
U.S. Pat. No. 2,936,008 to Brown teaches a mobile chipping unit capable of producing flat wood chips from whole trees.
U.S. Pat. No. 2,969,095 to Bookhyser et al. teaches a feeding apparatus for a rotary wood flaker used in producing wood flakes for hardboard.
U.S. Pat. No. 3,032,281 to Wexell teaches a wood chipping machine having a rotatable chipper disc carrying a plurality of circumferentially spaced cutter knives with a particular securing means to secure the knives to the disc. Wexell teaches an elongated bolt head to ease in securing the knives to the disc and thus decrease the machine down time.
U.S. Pat. No. 3,237,663 to Kirster discloses a wood chipping apparatus for making chips where the feeding channel is designed to guide the wood pieces to the cutter so that the pieces will be cut either parallel or perpendicular to the wood grain.
U.S. Pat. No. 4,346,744 to Beer et al. teaches a wood waferizing apparatus designed with cutter knives that hold the wood piece stationary and cut it substantially parallel to the wood grain.
U.S. Pat. No. 4,298,044 to Hansel et al. teaches a wood chipper having angularly space knife blades mounted on a rotating disc. The angularly spaced knife blades are adjacent to angularly spaced passageways where the wood is fed to the other side of the disc.
U.S. Pat. No. 4,685,497 to Mierau et al. teaches a wood waferizing apparatus having serrated, staggered disposable knives.
The above mentioned art discloses methods and machinery for producing flat wood chips, flakes or fibers. The rake angles used in the cited prior art are substantial.
The present invention is related to but distinct from disc flakers known in the prior art. The present invention, unlike the prior art, utilizes a relatively small rake angle to produce a wood curl instead of a flat wood chip or flake. Another factor important in producing durable and substantial wood curls is wood grain orientation. A notation developed by W. M. McKenzie and published in Fundamental Analysis of the Woodcutting Process by Peter Koch (Ronald Press Company, 1964, p. 36), is useful in describing wood grain orientation in the orthogonal cutting situation. This system consists of two numbers separated by a hyphen. The first number is the angle the cutting edge of the knife makes with the grain of the wood (hereinafter "cutting angle"). The second number is the angle that the tool motion vector makes with the grain of the wood. The vast majority of chippers and flakers known in the prior art have a cutting action described by the referenced nomenclature as 0-90. This means that at each instant as the blade moves through the wood its cutting edge is parallel to the grain but the motion of the blade is perpendicular to the grain. The cutting action for the present invention, in contrast, is described in accordance with the referenced nomenclature as 90-5. This means that the knife edge is perpendicular to the grain and the knife motion is at a slight angle to the grain.
Curled wood flakes have many applications. Predominant uses are for packing and potpourri material. A commonly used packing material is polystyrene in the form of peanuts, worms, and shells. Although polystyrene has certain qualities which render it suitable for packing material, it has come to be recognized as an environmentally harmful substance. The chemicals used in the production of polystyrene are associated with depletion of the ozone layer of the atmosphere. Polystyrene is not biodegradable.
Long, thin, grass-like wood shavings, sometimes referred to as excelsior or wood wool, have also been used as packing material. Such material does not readily conform to the shape of the packaged object. Therefore, more labor is required to package an object with it. Such material also releases dust particles which may damage the packaged item and be untidy.
Paper is also used as a packing material. It is not as readily disposable as either excelsior or the wood curls produced by the present invention. Also, it may be necessary to use an amount of paper having a greater than desirable bulk density in order to adequately protect the packaged item.
Curled wood shavings produced in accordance with this invention are lightweight, relatively dust free, elastic, inexpensive and environmentally safe to manufacture and use. Curled shavings can be poured around an object being packed. They conform to its shape and require less manual arrangement than excelsior-like materials.
A second important application for wood curls is for potpourri materials. Traditionally, potpourri mixtures have been comprised of dried herbs and flowers. Recently, other materials such as stone, ceramic pieces and wood shavings have been treated with fragrant oil and added to potpourri. The wood shavings currently used in potpourri are typically flat wood scraps from industrial wood peripheral milling operations. These scraps tend to break up and splinter. They are also not very decorative and do not enhance the appearance of a potpourri mixture. Curled shavings are very decorative. They are also far more elastic and less subject to splintering than flat wood scraps. Curled shavings have greater surface area than flat wood scraps and therefore emit more fragrance.